Rivermatics

USGS Streamgage 11051500

Santa Ana River near Mentone, CA

Santa Ana River near Mentone, CA is USGS streamgage 11051500 in California, monitoring river discharge in hydrologic subbasin 18070203. It sits on the Santa Ana River, alongside 3 other gauges Rivermatics tracks on the same river. It drains a watershed of about 210 square miles. Discharge records at this site go back to 1891. Typical flow runs near 1.9 cfs in July and 19.3 cfs in April, with the higher of the two arriving in April. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead.

View live conditions & forecast →

Gauge details

State
California
Drainage area
210 sq mi
Gauge elevation
1,950 ft
Subbasin (HUC-8)
18070203
Coordinates
34.10834, -117.10059
USGS site number
11051500
Records begin
1891-02-23 (135 years)
Rivermatics forecast
14-day flow outlook

14-day flow forecast

Based on observations through for Santa Ana River near Mentone, CA. Each day carries a median estimate and the band the model expects the flow to fall within — not a single number to plan against. Forecasts are re-issued daily; see the live screen for the current outlook.

Forecast daily mean discharge in cubic feet per second, by date
Date Low p10 Expected p50 High p90 Range
39.2 41.8 43.6
33.8 40.4 44.1
29.2 39 44.4
25.3 37.7 44.7
22 36.6 44.9
18.2 35.6 45.1
20.3 34.9 45.2
18.9 34.2 45.4
14.5 33.5 45.9
11.7 32.6 46.1
12.7 32.2 45.6
15.4 31.8 46.8
13 31.6 46.5
10.1 31.3 47

All values in cubic feet per second (cfs). Estimates only — do not use them for navigation or for any safety, rescue, or emergency decision.

Typical flow by month

Long-term daily discharge percentiles from the USGS record (up to 130 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month Low p10 Typical p50 High p90 Range
January 0 4.2 82.6
February 0.7 8.2 176
March 1 12.7 247
April 0.8 19.3 228.2
May 0.4 7.2 168.2
June 0.1 2.5 96.9
July 0 1.9 60.9
August 0 1.5 36
September 0 1.2 27.7
October 0 1.3 30.4
November 0 1.8 24
December 0 3 37.7

All values in cubic feet per second (cfs).

Common questions

When does Santa Ana River near Mentone, CA normally run highest?
April, on the long-term record. The median daily flow that month is about 19.3 cfs, against 1.2 cfs in September, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
What is a normal flow for Santa Ana River near Mentone, CA?
It depends on the month. In January, half of days historically fall near 4.2 cfs, with the middle 80% of days between 0 and 82.6 cfs. The month-by-month table on this page gives the full range.
How long has Santa Ana River near Mentone, CA been measured?
Discharge records at USGS site 11051500 begin in 1891, about 135 years, covering roughly 9,130 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
Is there a flow forecast for Santa Ana River near Mentone, CA?
Yes. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on this basin's observed flows, weather, and snowpack, and issues a daily flow outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on the live gauge screen. Open live conditions to see the current outlook.
Where is Santa Ana River near Mentone, CA?
The gauge sits at 34.10834, -117.10059, in California, in hydrologic subbasin 18070203, at an elevation of about 1,950 feet, draining roughly 210 square miles.
Can I use Santa Ana River near Mentone, CA data for flood or safety decisions?
No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

Upstream and downstream on the Santa Ana River

Every gauge Rivermatics tracks on this river, ordered by drainage area — upstream first. See the Santa Ana River in full.

Other gauges in this subbasin